Updating Datagrid

I have a datagird in my windows form.   l'm having problems updating the dataset and writing back to the database.   On a mousedown event I want to add the username and date.  This works.   I then need to write in some comments then update the datagrid.   My problem is that it will not update.

 pt = New Point(e.X, e.Y)
        Dim testdate As String
       Dim hti As DataGrid.HitTestInfo = DataGrid2.HitTest(pt)
        If hti.Type = DataGrid.HitTestType.Cell Then
            DataGrid2.CurrentCell = New DataGridCell(hti.Row, hti.Column)
            DataGrid2.Select(hti.Row)
            DataGrid2.Item(hti.Row, 2) = UserName 'Column 3
            DataGrid2.Item(hti.Row, 1) = Now 'Column 3

        End If